Re: HDLC frames delivered over PWs

Hello Javi,

Please see inline.

On 9/7/2006 6:40 AM, Javi allegedly said the following:
> Hello Carlos,
> 
> Thanks, I agree with you.
> 
> Howerver, my question tried to evaluate the efficiency of the method. If 
> PWs deliver all HDLC frames, it means all RR/RNR frames (which are 
> continuously transmitted)
> 
> So, HDLCPW would use too much resources in the IP network. Is it 
> neccesary?. Perhaps, delivering only "I" frames may be enough if we use 
> polling in LCCEs (so that, they answer to RR/RNR frames).

The HDLCPW encapsulation does not inspect a frame incoming on the AC
beyond HDLC flags and FCS, to maximize transparency.

This for instance allows what's described in the rfc:

   Since all packets are passed in a largely transparent manner over the
   HDLCPW, any protocol that has HDLC-like framing may utilize the
   HDLCPW mode, including PPP, Frame-Relay ("port to port" Frame-Relay
   transport), X.25 (LAPB), etc.  In such cases, the negotiations and
   signaling of the specific protocols transported over the HDLCPW take
   place between the Remote Systems.
...
   In addition
   to the transport of HDLC frames, a natural application of HDLCPWs
   allows for the transport of any protocol using an HDLC-like framing.
...
      o HDLC data and control fields are transported transparently (see
        Section 4.1).  The specific negotiations and signaling of the

This is in turn in line with the PWE3 Architecture in rfc3935.

Thanks,

--Carlos.

> 
> Thanks,
> 
> Javier Muñoz
> 
> 
> Carlos Pignataro escribió:
>> Hello Javi,
>>
>> All frames (think of it as a pseudo-wire); you can refer to RFC4349,
>> first paragraph of Section 4.1 and first bullet of Section 5:
>>
>> http://tools.ietf.org/html/rfc4349#section-4.1
>>
>>    The HDLCPW Type over L2TP is
>>    intended to operate in an "interface to interface" or "port to port"
>>    fashion, passing all HDLC data and control PDUs over the PW.  The
>>    HDLC PDU is stripped of flags and trailing FCS, bit/byte unstuffing
>>    is performed, and the remaining data, including the address, control,
>>    and protocol fields, is transported over the PW.
>>
>> http://tools.ietf.org/html/rfc4349#section-5
>>
>>       o HDLC data and control fields are transported transparently (see
>>         Section 4.1).  The specific negotiations and signaling of the
>>         protocol being transported are performed between Remote Systems
>>         transparently, and the LCCE does not participate in them.
>>
>> Thanks,
>>
>> --Carlos.
>>
>> On 9/4/2006 4:37 AM, Javi allegedly said the following:
>>   
>>> One question related to transport of HDLC (or LAPB) frames over L2TPv3
>>> (+PWE3):
>>>
>>> What HDLC frames are delivered over PWs?, only frames I (Information),
>>> also RR and RNR, or all frames. It is a very important efficiency
>>> factor. For instance, RR frames are continuously send, it would consume
>>> too bandwidth in IP network.
>>>
>>> Javi Muñoz
>>>
>>>
>>> _______________________________________________
>>> L2tpext mailing list
>>> [email protected]
>>> https://www1.ietf.org/mailman/listinfo/l2tpext
>>>
>>>     
>>   
> 

-- 
--Carlos Pignataro.
Escalation RTP - cisco Systems